Selective hydrogenation of diolefins

ABSTRACT

Diolefins, present in minor amounts, in gaseous feed streams, particularly those to be used in alkylation reactions are selectively converted to mono-olefins by hydrogenation over sulfided nickel-tungsten catalyst.

United States Patent Chomyn 51 Oct. 3, 1972 SELECTIVE HYDROGENATION OF3,472,763 10/ 1969 Cosyns et al ..208/255 DIOLEFINS 3,234,298 2/1966Langhout et al ..260/677 H 2,595,772 5/1952 Daussat et a]. ..260/683.9[72] Invent Karl 3,177,159 4/1965 Rodgers et a1 ..260/683.9 [73]Assignee: Esso Research and Engineering Company Primary Examiner-DelbertE. Gantz Assistant Examiner-Veronica OKeefe [22] Filed March 1970Attomey-Pearlman and Stahl and C. D. Stores [21] Appl. No.: 22,792

1 [57] ABSTRACT [52] US. Cl ..260/677 H, 260/683.9, 208/255 Diolefins,present in minor amounts, in gaseous feed [51] Int. Cl ..C07c 5/06streams, particularly those to be used in alkylation [58] Field ofSearch ..260/677 H, 683.9; 208/255 4 reactions are selectively convertedto mono-olefins by hydrogenation over sulfided nickel-tungsten catalyst.

[56] References Cited UNITED STATES PATENTS 4 Claim, 2 Drawing FiguresP'ATEN'TEDncI 3 1972 3,696,160

sum 1 or 2 REACTION RATE CONSTANT VERSUS lO /T C CONVERSION IOODr-SYMBOL H /DIENE RATIOS I:I o.s4-|.o4

II Q X,

.10 I I I -I v I I l I0.0 no 2.0 13.0 14.0 5.0 16.0 |?.0

INVENTOR.

KARL D. CHOMYN BY FIG. I.

' ATTORNEY PATEN1E1111111 11112 I 3,696,160

SHEET 2 0F 2 REACTION RATE CONSTANT VERSUS lO /T C ==CONVERSION I0.0

SYMBOL 1-1 DIENE RATIOS CI 0.84-1.04 O o |.64- 2.32 O A 4.7-5.75

II II 4 1 INVENTOR.

ATTORNEY BACKGROUND OF THE INVENTION This invention relates to theselective hydrogenation of diolefins in hydrocarbon streams containingmonoolefins and is especially concerned withselective conversion ofpropadiene and butadiene contaminants in propylene and butene chargestocks employed in alkylation process for the production of aviation andmotor gasoline wherein the feed stock is contaminated with sulfur. It isalso useful for the selective conversion of C diolefins to mono-olefins,e.g. butadienes to butenes.

The C;,/ C, fraction employed in alkylation processes is principallythat obtained from thermal or catalytic cracking of higher boilinghydrocarbons or from a hydrocarbon coking operation; the C l C cut istaken over a practical boiling range so as to be substantially free of Chydrocarbons, although minor amounts of these may be present byentrainment or otherwise. Such C l C fraction may generally contain inthe order of about 0.3 percent and up to about 2 percent or more byweight of diolefin; the C;,/ C, fraction from a cracking operationrarely contains as much as 2 percent of diolefin. Even this smallcontent of diolefin in the feed for the alkylation process has beenwidely recognized as being extremely undesirable for the one reason,among others, of the greatly increased consumption of acid madenecessary thereby, as a result of forming tarry acid-diolefincondensation products, adversely affecting the over-all economics of thealkylation process. Several suggestions for the conversion or removal ofthe diolefins from hydrocarbon mixtures also containing monoolefins havenot proved attractive, because of accompanying concomitantdisproportionate loss of mono-olefins in the treated product, and highoperating and investment costs.

In the case of a C C fraction derived from a coking operation which maycontain'even higher proportions of diolefins, going up to 5 percent ormore, the problem is even more acute, and the use of such fractions foralkylation has been largely avoided.

Among the suggestions made to overcome the above difficulties is theproposal made in US. Pat. No. 3,1 13,983 to Kirsch et al., issued Dec.10, 1963, wherein diolefin contaminants are selectively hydrogenated toolefins in an alkylation feed by passage of the feed over a sulfidedcobalt molybdenum catalyst supported on A1 0 Unfortunately the use ofsuch catalysts has several drawbacks.

l. Relatively high operating severity is required (pressure 200-400psig, temperatures higher than 400 F.

2. To maintain the catalyst activity at the desired Supported nickel andpalladium catalysts are excellent hydrogenation catalysts in thediolefin conversion service. However, they display very low tolerance ofsulfur in the fresh diolefin feed. Consequently, their use is limited tosulfur-free feedstocks.

SUMMARY OF THE INVENTION In accordance with the present invention, theselective conversion of diolefins to olefins, particularly in feedstocks containing sulfur, is accomplished by effecting the hydrogenationover a catalyst comprising sulfided nickel-tungsten on an inert supportsuch as alumina, kieselguhr, silica-free clay, bauxite, mullite, etc.,alumina being preferred.

DETAILED DESCRIPTION The process of the invention involves passing ahydrocarbon stream containing minor amounts of diolefins and sulfur overa sulfided nickel-tungsten catalyst on alumina or other support. A C l Cstream is of particular interest in this connection.

The catalyst contains 4 to 6 wt. percent nickel, 14 to 20 wt. percenttungsten and the balance A1 0 The tungsten to nickel ratio is preferably4/1 to 5/1. The catalyst is sulfided with H 8 or CS to prior to use.

The above catalyst has been found to have a remarkable degree ofselectivity in that it is active for the hydrogenation of diolefins tomonoolefins but relatively inactive for the hydrogenation ofmono-olefins to paraffins in the temperature range of 200400 F pressure-200 psig and hydrogen/diolefin ratio of Hi to 6.1.

While the greatest advantages of the described process are obtained inthe treatment of olefinic C l C hydrocarbon streams containing about 2percent butadiene by weight of total hydrocarbons, the process is alsoapplicable, but not necessarily with equal results, to the treatment ofolefinic C C fractions of higher diolefin content, such as abutane-butylene fraction obtained from a thermal coking operation whichmay include up to about 5-6 percent diolefins. A further application ofthe invention lies in the treatment of a butylene-rich stream from adehydrogenation process containing from a fraction of a percent up toabout 5 percent diolefin. For example, in the dehydrogenation of butane,for production of butadiene, particularly after separation of theproduct butadiene by fractionation and extraction, there still remainsin the monoolefin-rich raffinate a small percentage of butadiene of fromabout a fraction of a percent up to about 2 percent depending upon theefficiency of the separation. This small amount of butadiene cannot beeconomically recovered as such, and interferes with the possible uses ofthe raffinate, for instance as feed to alkylation. Some butadiene isalso produced in those processes designed principally for conversion ofbutane to butene. If the quantity of butadiene in the product issufficiently great, say in excess of about 5 percent its recovery byknown procedures may be warranted. Smaller quantities of butadiene, asbetween about 3 to 5 percent may or may not be worth recovering as such,depending upon recovery costs versus market demand and value. In eitherof the above instances, the enhancement of the butene product byselective hydrogenation of diolefins in accordance with the presentinvention, comes into consideration.

The selective hydrogenation of propadiene/butadiene in amono-olefin-rich mixture by the present invention is more easilyaccomplished and with greatest efficiency when the proportion ofdiolefin in the mixture is quite low, for example about 2 percent. Insuch instance catalytic hydrogenation under the describedSPaWfVCIOCiIILSCFH OfFeeMEX- 01 [000 N cu. t. cata yst etc 1) operatmgconditions can be accomphshed 1n isother- Gas Ram, Mole Iii/Mole Diem-m2240/ (Note 2) mal or ad1abat1c reactor systems, and some var1at1onPressure at Inlet to Preheat Exchanger, psig 175 from the optimum inprocess variables can be tolerated at the expense of some sacrifice inyield and purity of produpt' Note 1 Some variation in liquid hourlyspace velocity (LHSV) oc- To illustrate the benefits of the invention,feeds havcurred in lab. The range of LHSV was 2.8-4.0 V/HrJV. ing thefollowing composition Note 2 Hydrogen to diene ratios were varied from1.0 to 6.0

TABLEI The data were analyzed on the basis of a first order kineticsexpression to calculate the constants KC FEED INSPECTIONS and KC, anddefined as follows:

Composition, Wt.% Sample 1 (Note 1) Sample 2 (Note 1) Propane 6.46 6.71K: S[In(1-x)] Propylene 13.24 13.75 n-Butane 22.79 lso-Butane 7.l6Butene-l 26.30 26.08 I lsobutylene 1.61 1.56 where- Propadiene 1.39 1.46lsopentane 2.94 2.86 "9" i g' 2% 22? S space velocity and x is thefraction of reactant ClS uenen-Pentane 0,01; 08 converted 1nto product.y B 3 The effects of the operating temperature on the 53,??? 83g 2hydrogenation of propadiene and butadiene are shown Total 100.00 100.0030 in FIGS. 1 and 2, where FIG. 1 is an Arrhenius plot forcumnylsulfifle'wppM 33-57 '(Nmez) the propadiene conversion and P16. 2for butadiene Molecular Weight 53.8 (Note 2 Specific Gravity 0.572 Note2 convers1on, the data bemg set forth 1n Tables 11, Ill, and

TABLE I[.SUMMARY OF OPERATIONS Catalyst Ni-W 011 A1203, (10 00., 8-14Mosh c 't' i igs ifm, p.s.i.g 175 175 175 175 175 175 100 170 175 175105 175 [e1np0r21tur0, F 100 205 257 270 255 270 305 233 300 2140 350Feed rate, (gas) liters/hr 50.0 53.0 50.7 50.7 53.1 43.4 30.7 40.1 40. 455.11 51.1 Feed rate, (liquid) v./l11'./v 3.05 1.15 3. 06 3. 06 3. 733.3!) 2. 3. 36 2.81 6.112 3. 0;? Hydrogen feed, 1it0rs/l11'.. .2. 8 7. 82.11 7. 8 2. 6 7. 8 2. G 1.3 2. 3 1. 3 2.11 11211115115 ratio 1.77 4.71.04 1.0 1.77 5.75 0.31 1.30 1 1 k=l 1-.

i t linhii w, 0. 5115 0.331 1. 13 1.211 3.35 13111111110110, k 0.550.381 0.73 0 4 15 3,311 lrodnct analysis, wt. porcunt: I r lmpnnu (i. 111 (i. 11. 21 11. 111 11. .11 l'l'opylonu 13.63 14.13 12.02 13.11 13.1!lsohutzult 23.511 23.76 23.31 23. 78 23.1 n-liutanv. 7.25 7.1111 7.457.32 7.10 llutunu-l 25.110 .25. 75 26. 53 20.30 21. 1 lsobutylullu 1.881.85 1.8.) .811 1.111 1.813 lropadiene 1. 20 1. 27 1). 111 .83 1. 00(1.14 101101110 2.110 2.74 3.13 .30 2. 35 3.05 011105115 2 0.32 3. 700.33 ..00 11. 07 10.3 0141051102 0.20 0.00 0.05 0.00 0.37 0.311 7. 314 13-l)utad1cnc 0.81 0. 31 0.75 0.02 0. 0.70 0.33 0. 37

-3: 112 .13; 0 1.1 3' 1,0 1"; s 0.24 0. 1 .2. 40.71 40.05 40.31 50.1051.40 40.55 51.07 50.1 1110151111 input, liters/h 1.58 1.47 1.35 1.121.34 1.13 1.55 1.4 1 1 83313125... 13.7 8.6 34.5 47.5 30.0 40.2 23.0 00.0 (11010150115 13 0.7 10.4 3 14.4 24.0 10.7 00.5

Note 1 Duplicate analyses.

Note 2 Not determined.

were hydrogenated at various temperatures and under the followingconstant conditions:

2. The process of claim 1 in which the feed stream contains C3 and C4diolefins.
 3. The process of claim 1 in which the diolefin content ofthe feed stream is less than 2 percent.
 4. The process of claim 1 inwhich the tungsten-to-nickel ratio is said catalyst is between about 4/1to 5/1.